Determination of densities of fluids in wells



March 1%, 1941. R. T. CLOUD DETERMINATION OF DEHSITIES OF FLUIDS INWELLS Filed July 16, 1938 INVENTOR Raymond T Cloud ATTORN EY ill tlutentecl Mar. 18, 1941 cannot ltaymond T. llloudt Tulsa, @tlllldh,assignor to Stanolind illil and Gas llompany, Tulsa ulrlla, acorporation oi Delaware This invention relates to means for thedetermination of the specific gravities, densities or relative densitiesoi well fluids and more particularly oi the fluids present in oil wells.

it is an object oi my invention to provide apparatus which will permitthe measurement oi the densities of well fluids at varying depths withina well. Another object of my invention is to provide apparatus of thistype which can he operated quickly and conveniently and which will givereadings at or above the surface oi the ground. A further object is topr'ovide appara tus io-r logging a well by the determination oi thedensities of the fluids within it. it still ther object of my inventionis to provide a device for the determination of the point oi gas, oil orwater intrusion into a well. Additional objects, advantages and uses oimy invention will become apparent as the description thereoi proceeds.

The device of my invention. includes an cle merit responsive to thedensity oi the well fluid surrounding it and means tor indicating and/orrecording this density. Freierahly this indication or recording is madeat the surface oi the well.

fluch a device has many important uses in connection with oil wellpractice. Thus tor in stance, one method of using such a device is inthe logging of here holes. This can he done hy circulating a drillingmud, preferably one having a high specific gravity, within the well andthen lowering the head of the liquid in the well, tor instance h-ypumping or hailing out a portion oi the drilling mud. This reduction inhydrostatic head permits the fluids contained in the iorma tionspenetrated by the well to enter the here hole. hy the use of my devicethe speciflc gravity oi the column of liquid can then be measured atvarious depths or continuously as the device is raised and lowered.Where the measured spe ciflc gravity is that of the circulated mud, itis obvious that no fluid has entered the well hut when the specificgravity is found to have heen lowered it is indicated that fluids fromthe strata opposite such points have entered. it the opeciiic gravityhas been lowered hut does not tall helow unity or below the gravity ofoil-held hrines it is apparent that water or brine has entered at thispoint but where the gravity has fallen to less than unity, it isapparent that oil has entered orin some instances that gas has enteredand become emulsified with the drilling mud.

Further, a device of this type is useful in that it permits the rapidand accurate location oi the water-oil interface within an oil well and.this is (UL Eddld) an advantage in bottom. hole sampling work. Thedevice can also be used to determine the densities oi fluids in thebottoms of so called distillate wells and to locate accurately the fluidlevels in such wells. It can likewise he used in 4% running tests withina well to determine the elfiect oichanges in pressure, etc. on fluids,particularly fluids oi the distillate type, present within a bore hole.

The invention will now he described in more detail in connection withthe accompanying drawing which terms a part oi this specification and isto he read in conjunction therewith. in the drawing: Figure l is adiagrammatic elevation of a por-- tion oi a bore hole and the equipmentabove it, illustrating in highly simplified form one em hodiment oi myinvention;

Figure 2 is a sectional elevation of a preferred embodiment oi thatportion or my apparatus which is used within the well;

Figure ii is a sectional elevation taken along the line oi Figure 2;

Figtu'e d is another sectional elevation taken along the line of Figure2; and

Figure 5 is a highly simplified diagrammatic elevation showing theunderground portion oil a modified iorrn of apparatus in accordance withmy invention.

Turning to Figure i, it will he seen that a bore hole it penetratesheneath the surface oi the earth ill and that the device is lowered intothis here hole to measure the speciflc gravities or densities of thefluids within it, Essentially this device consists ot a weight it actingon a spring l t; The strain occasioned by the weight is, of course,proportional to its effective or apparent weight in the particular fluidin which it is immersed. The result is that varying fluid speciflcgravities vary the point of contact between contactor it and resistanceit.

insulated electrical conductors and supporting cables Ill, it and it areraised and lowered together' by means of hoist it. While these are shownas three separate lines they will in practice usually he a singlesupporting cable containing three insulated conductors.

From hoist it the electrical circuits pass through slip rings (notshown) to conductors it, it and it which are extensions of conductorsll, it and it respectively. A source of voltage 24 is connected acrossconductors t2 and 23. Conductors it, it and it lead to a resistanceratio type of telemetering device 25.. This device contains two coils 26and 21 mounted on a common shaft at right angles to each other. Thesecoils are placed in a magnetic field provided by magnet 28.

It will be apparent from the circuits shown that the currents flowingthrough the two coils will vary in accordance with the position ofcontactor I 5 on resistance It since the circuit which includes coil 23contains that portion of resistance I6 which is below contactor I5 whilethe circuit which includes coil 21 contains that portion of resistanceI6 which is above contactor l5. The difference in current flow throughthese two coils tends to cause them to rotate in the magnetic fieldprovided by magnet 28 and this rotation is opposed by spring 29 which isanchored at post 30. The amount of rotation is a function of thespecific gravity of the fluid in which weight I3 is immersed and thisdegree of rotation is shown on scale 3|. Itwill be apparent that thisscale can be calibrated in arbitrary terms, in specific gravity, inpounds per gallon or in any other desired unit.

It will also be apparent that other types of telemetering devices arewell known and can be used and that my invention is by no means limitedto the use of the resistance ratio type of device.

' As an illustration of the variation in apparent weight to be expectedfrom a device of this type we may consider the case of an aluminum blockhaving a volume of 100 cubic inches lowered into a well which containsmud weighing 11 pounds per gallon. The weight of the block in thisinstance is 9.7 pounds in air while the apparent weight in the mud,water and oil (specific gravity .65) is as follows:

Apparent weight, pounds Circulating mud 4.94 Water a 6.1 Oil 7.4

The underground portion of one form of my device is shown in Figures 2,3 and 4. In Figure 2 it will be seen that a case 32 which can suitablybe made from some insulating material of the synthetic plastic type isdivided into two compartments 33 and 34 by means of partition 35. Meansfor access to these compartments are, of

course, provided but are not shown inthese views.

Compartment 33 is open to the well fluids through holes 36 and 31 whilecompartment 34 is filled with a relatively non-compressible insulatingliquid such as transformer oil and is kept out of contact with the wellfluid by means of gland 38 which will be described in. detailhereinafter. Weight I3 is supported from arm 39 which is rigidly mountedon shaft 40 carried between bearings 4| in such manner as to give aminimum resistance to rotation. This rotation is opposed by coil springI4 anchored to post 42.

The shaft also carries a contactor arm I5 (best seen in Figure 3) whichmakes contact with resistance I6. From the two ends of this resistanceinsulated conductors l8 and I9 lead out of compartment 34 through doubleheaded binding posts 43 and 44 and thence into 3-conductor cable 45which supports case 32 and its contents through U-bolt 46 and passes atits upper end to hoist 20. Similarly, a third insulated conductor I1leads from a point in metallic contact with contact arm I5 throughdouble headed binding post 41 to 3-conductor cable 45. It is of courseunderstood that the outside portions of these double headed bindingposts must be insulated from contact with well fluids.

Gland 38, to which reference has previously been made, serves thepurpose of keeping well fluids out of compartment 34 and at the sametime makes it possible to maintain the same pressure in compartment 34as in compartment 33, thus preventing fracture of the case 32 orpartition 35 due to varying well pressures as the device is raised orlowered. Ring 48 is attached to shaft 40 and to it is claimed a flexibleoilresistant tube 43. This clamping is done by ring 50 which is equippedwith flanges 5! which'are pulled together by means of bolt 52 as can beseen in Figure 4. The other end of this flexible tube is clamped bymeans of ring 53 to a projection 54 on partition 35. Flexible tube 49can be made of a synthetic oil-resistant rubber composition such asDuprene or Thiokol. It is of such length and sufiiciently thin as tooffer very little resistance to the rotation of shaft lll within thelimits required and is also sufliciently flexible to permit equalizationof the pressures in compartments 33 and 34.

It will be apparent from this description of one embodiment of myinvention that the specific gravity of the fluid within the well at thelevel of the specific gravity-responsive device will control the forceoperating on weight I3 and thus give an indication or record of thespecific gravity of the well fluid. However, it is not essential to relyon measurements of weight forces in order to determine the specificgravities of liquids encountered in the well since the density of theliquid column is a function of the pressure differentials encountered intraversing this column. Thus 'Q d 2 p Where p=pressure z=depth p:density or the rate of change of pressure with depth is proportional tothe density of the liquids at the point where the readings are taken, sothat if two pressure devices separated by a small distance are loweredinto the well arranged so as to record the differential pressure betweenthe two devices the density or specific gravity of the liquid columnincluded between the two pressure devices, will be proportional to thereadings obtained.

A device of this type is shown in Figure 5 which is confined t0 thesub-surface portion of the equipment. A telemetering' device and otherabove-surface equipment identical with that shown in Figure 1 can beused. The device of Figure 5 includes two compartments 55, each of whichhas a diaphragm 55. The forces exerted on these diaphragms are, ofcourse, proportional to the pressures of the well fluids on the outsideof them. These forces tend to rotate contactor arms 57 and thus vary thepositions of these contactors on resistances 58. Conductors I'l, I8 andI9 corresponding exactly to the conductors of the same numerals inFigure 1 lead to the abovesurface equipment and specific gravity canthus be measured by the device of Figure 5 just as in the case of thedevice of Figure 1.

While I have described my invention in connection with certain preferredembodiments thereof it is to be understood that these are by way ofillustration and not by way of limitation and I do not mean to belimited thereby but only to the scope of the appended claims.

In the claims, where density measurement is referred to, I mean toinclude also the measurement of specific gravity, relative density, etc.and

where I speak of indicating values of this type '1 also mean to includethe recording of such values.

I claim: ii i. A device for determining well fluid density whichcomprises a weight suspended in said well fluid, a spring opposing theforce exerted by gravity on said weight, means responsive to theposition of said weight under the influence of lo gravity, means forraising and lowering the foregoing elements within a well and meansassoci- 'ated with said responsive means for forming an indicationcorresponding to the position of said weight. w 2. A device fordetermining well fluid density which comprises a weight suspended insaid well iluid, a spring opposing the force exerted by gravity on saidweight, means responsive to the pbsition of said weight under theinfluence of 2 gravity, means for raising and lowering the foregoingelements within a Well and telemetering means to produce above thesurface of the ground an indication corresponding to the density of thefluid in which said weight is immersed.

3;. A device for determining well fluid density which comprises a weightconstructed and arranged to be inserted in a well, means constructed andarranged to be inserted in said well and to suspend said weight in thefluid present in said well, a spring associated with said Weight andsaid means and constructed and arranged to be inserted in said well foropposing the force exerted by gravity on said weight, a contact armr-esponsive to the position of said weight, a resistw ance contacted bysaid contact arm, means for maintaining said resistance and the contactarm in contact therewith out of contact with said well fluid to preventshort circuiting of said resistance, and means associated with saidresistance and ill said contact arm for forming an indicationcorresponding to the position of said weight.

i. A device for determining well fluid density which comprises a weightconstructed and arranged to be inserted in a well, means constructed i5and arranged to be inserted in said well and to suspend said weight inthe fluid present in said well, a spring associated with said weight andsaid means and constructed and arranged to be inserted in said'well foropposing the force exerted til by gravity on said weight, a contact armconstructed and arranged to be inserted in said well responsive to theposition of said weight, a resistance constructed and arrangedto beinserted in said well contacted by said contact arm, means 55 formaintaining said resistance and the contact arm in contact therewith outof contact with said well fluid to prevent short circuiting of said resistance, telemetering means associated with said resistance and saidcontact arm for forming above the surface of the ground an indicationcorresponding to the position of said weight and means for-raising andlowering said weight, said contact arm and said resistance in said well.

5. A device for determining the densities of well fluids comprisingmeans responsive to the pressure of well fluids at one level, meansresponsive to the pressure of well fluids at a second level, means forproducing electrical variations in accordance with the differentialresponse of said two responsive means and a telemetering deviceassociated with said last-mentioned means for indicating above thesurface of the well the density of the fluid in which said tworesponsive means are immersed.

6. Apparatus for logging a well comprising density-responsive meansadapted to be inserted in a well, means for lowering saiddensity-responsive means into said well, means associated with saiddensity-responsive means and adapted to be inserted in a well forproducing electrical variations in accordance with the varying responseof said density-responsive means, means for transmitting said electricalvariations to the top of said well, and means associated with thelast-mentioned means and located above the surface for indicat ing therelative densities at various depths of the fluids in said well in whichsaid density-responsive means is immersed.

7. A device for determining well fluid density which comprises twocompartments, one of said compartments being open to the penetration ofwell fluids and theother being closed to the penetration of well fluids,a substantially fluid tight seal between said two compartments, adensityresponsive member disposed in the first of said compartments,means yieldingly opposing the movement of said density-responsivemember, force transmission means associated with said density-responsivemember and passing through said seal, a contact arm associated with saidforce transmission means disposed within the second of said twocompartments and responsive to the position of said density-responsivemeans, a resistance contacted by said contact arm disposed within thesecond of said two compartments, all of the previously mentionedelements being constructed and arranged to be inserted in a well, meansfor raising and lowering said elements within said well, andtelemetering means associated with said resistance and said contact armfor forming above the surface of the ground an indication correspondingto the position of said density-responsive means.

RAYMOND T. CLOUD.

